There currently is a tendency to manufacture integrated circuits performing more and more complex functions, in ever-increasing numbers. This results in an increase in the heat dissipated in the integrated circuit. For reasons of performance and reliability, it is often necessary to provide a device for controlling the integrated circuit temperature to maintain the circuit within an acceptable temperature range. The control device generally comprises a temperature sensor made in integrated fashion.
The temperature sensor typically must comply with several constraints:                it typically must provide a signal representative of the integrated circuit temperature in a readily-usable digital form;        it typically must provide a signal representative of temperature with a sufficient accuracy;        it typically must operate properly in a noisy digital environment;        the sensor setting, or calibration, typically must be simple; and        the sensor manufacturing method typically must be compatible with CMOS manufacturing processes.        
To comply with such constraints, different temperature sensor circuits have been provided.
FIG. 1 schematically shows a conventional embodiment of a temperature sensor 10 providing a signal representative of temperature in digital form.
Sensor 10 comprises a temperature-measurement unit 12 (TEMP. SENSOR) providing an analog signal ST representative of temperature. An amplifier 14 (A) receives signal ST and provides an amplified signal AST. An analog-to-digital converter 16 (A.D.C) converts signal AST into a digital signal Code, coded over N bits, representative of temperature. The operation of converter 16 generally requires a constant reference signal SREF provided by a reference signal generation unit 18 (REF.GEN).
Typically, signal ST corresponds to a voltage varying between 45 and 75 mV, respectively for −40° C. and +125° C., which represents a 30-mV variation. Most analog-to-digital converters require for the analog voltages which are provided thereto to be within a range from 0 to 1 V. It thus may be necessary for amplifier 14 to have a high and accurate amplification factor. Indeed, an inaccuracy at the level of amplifier 14 would translate as a significant inaccuracy of the provided digital signal Code. Further, amplified though it may be, signal AST keeps a limited slope, typically on the order of 5 mV/K. The forming of analog-to-digital converter 16 can then be critical. Indeed, if it is desired for the least significant bit of signal Code to represent 1 K, a 5-mV variation of signal AST must be translated by it. The forming of an amplifier 14 and of an analog-to-digital converter 16 of high accuracy typically translates as the obtaining of a temperature sensor 10 taking up a large surface area of the integrated circuit and having a high power consumption.